1. Field of the Invention
The present invention relates to a liquid crystal display device and a method for driving the same, in which a difference of data charge quantities is compensated in a liquid crystal display panel having a reduced number of data lines, for reducing power consumption.
2. Discussion of the Related Art
The liquid crystal display device displays a picture by using electric and optical characteristics of liquid crystals. The liquid crystal has an anisotropic characteristic in which both refractive indices and dielectrics in a long axis direction and a short axis direction of a molecule thereof are different from each other. The liquid crystal display device which utilizes those characteristic displays the picture by varying alignment direction of the liquid crystal molecules according to intensity of an electric field, thereby controlling a light transmissivity of a polarization plate.
The liquid crystal display device is provided with a liquid crystal display panel having a matrix of pixels, a gate driver for driving gate lines of the liquid crystal display panel, and a data driver for driving data lines of the liquid crystal display panel.
Each of the pixels on the liquid crystal display panel produces a desired color with a combination of red, green, blue sub-pixels which control the light transmissivities thereof in response to a data signal. Each of the sub-pixels is provided with a thin film transistor connected to the gate line and the data line, and a liquid crystal capacitor connected to the thin film transistor. The liquid crystal capacitor has a charge of a voltage difference between a data signal supplied to a pixel electrode through the thin film transistor and a common voltage supplied to a common electrode, and drives the liquid crystals according to the voltage charged thus for controlling the light transmissivity.
The gate driver has a plurality of gate integrated circuit (called as IC hereafter) for driving the gate lines of the liquid crystal display panel in succession.
The data driver has a plurality of data IC for converting a digital data signal into an analog data signal every time each of the gate lines is driven, and supplying the analog signal converted thus to the data lines of the liquid crystal display panel.
The data IC has complicate circuits, such as a digital-analog converter which costs high, and requires many data ICs more than the gate ICs since a number of the data lines are greater than a number of the gate lines in the liquid crystal display panel. Consequently, in order to reduce a production cost of the liquid crystal display device, a scheme has been taken into consideration, in which a number of the data ICs is reduced while a resolution of the liquid crystal display panel is maintained as it is.
For an example, in order to reduce a number of the data ICs, a liquid crystal display panel has been suggested, in which odd and even numbered sub-pixels positioned opposite sides of a data line are driven by the data line in succession for reducing a number of the data lines into one half.
However, in a case two dot inversion is applied for reducing power consumption of the liquid crystal display panel having a number of the data lines reduced by one half, a case can take place in which the sub-pixel is over charged due to a polarity thereof identical to a prior horizontal period and the sub-pixel is under charged due to a polarity thereof opposite to a prior horizontal period in longitudinal lines or transverse lines. In this case, a difference of data charge quantities takes place compared to the same gray scale between the overcharged pixel lines and the undercharged pixel lines, to cause a problem in which a poor picture quality, like longitudinal line or transverse line stains takes place. In order to solve the problem, a charge time period is reduced randomly in an overcharge period, i.e., data transition is made in the overcharge period to reduce the charge time period in the overcharge time period, so that the undercharge period and the overcharge period have an identical charge characteristic, as shown in FIG. 1. However, the random formation of a charge sharing section in the overcharge period causes to fail proper charge of the data, to cause to provide improper brightness. Moreover, the random formation of the transition sections in the overcharge time period leads to have more transition sections, which increases power consumption.